The present invention relates generally to motor mounting arrangement and to methods of making the same that are particularly useful in connection with mounting a motor to a bulkhead, baffle, or other suitable motor supporting structure of a product in which such motor is used. Examples of such products are: room air conditioners, air circulation fans, and so forth.
In direct drive applications, i.e., applications where blowers or fans are mounted directly to a motor shaft, it is important to isolate motor vibrations from the bulkhead or other mounting surface. It is, or course, desirable to minimize the transmission of all modes of vibrations; but for the reasons pointed out in detail in the above-referenced Litch application, it is especially desirable to minimize the transmission of noise associated with torsional mode motor vibrations. In particular, the noise associated with torsional mode vibrations of twice line frequency and harmonics thereof tend to be very objectionable.
The approaches suggested by Litch constitute advances in the art, although there may be some difficulty in applying those approaches. For example, there may be difficulty if the motor itself is manufactured by a process such that motor parts are secured together by structural adhesive materials; or if the motor is of relatively small mass and output, with the result that special manufacturing methods must be adhered to. More particularly, if a motor stator and bearing system is to be assembled and held together by a structural adhesive material such as epoxy (as taught, for example, in Thompson et al. U.S. Pat. No. 3,165,816, or Rutledge U.S. Pat. No. 3,195,222), it may not be desirable from a manufacturing standpoint to have mounting arms or lugs attached to the shell of the motor during the assembly process. Moreover, for motors of relatively small mass and diameter (and thus relatively small polar moments of inertia of the motor mass), where suitable torsional mode vibration isolation is to be accomplished by suitably reducing the transmissibility of the mounting arms or lugs or torsional mode vibrations, difficulties may be encountered because the dimensions of the motor mounting arms or lugs may have to be reduced to such a size that manufacture thereof may be difficult, specially if the radical length of the arms is to be relatively small.
When martensitic steel is utilized to support a relatively small motor (for example, a motor weighing about 2.7 kilograms and approximately three and eight-tenths inches in diameter), and the mounting bolt-hole circle is approximately seven inches in diameter; martensitic steel mounting arms should be only about 0.0010 of an inch thick for good torsional vibration isolation. However, material this thin generally would be difficult to handle in high volume manufacturing operations and often would not possess sufficient strength to withstand at least some shock loading conditions.
It will therefore be understood that it would be desirable to provide new and improved mounting arrangements for motors wherein such mounting arrangements are characterized by improved torsional vibration isolation characteristics, and yet which may be easily manufactured and assembled with motors that are secured together with structural adhesive materials.
Accordingly, it is a general object of the present invention to provide new and improved motor mounting arrangements and methods of making the same whereby the above-mentioned and other problems may be solved.
It is a more particular object of the present invention to provide a new and improved motor mounting arrangement and methods of making the same, that includes mounting arms which are made of material having sufficient thickness that the manufacture of such arms is facilitated and yet wherein the vibration transmissibility of such arms in objectionable frequency ranges is not objectionally increased because of the material thickness.
It is a further object of the present invention to provide new and improved motors and lug assemblies, as well as methods and means of interconnecting the same, that may be easily modified in order to tune the vibration transmissibility of the vibrating system formed of a motor and a plurality of mounting arms or lugs.